Chemistry Reference
In-Depth Information
TABLE 8B.14. Results with Prochiral
β
- Keto Esters and
β
-Diketones as Pronucleophiles in the
Allylic Alkylation according to Scheme 8B.30
a
O
O
O
O
O
O
O
O
OBn
OBn
OBn
OBn
MeO
95% ee (75%)
86% ee (81%)
95% ee (81%)
91% ee (98%)
L * = QUIPHOS (L24)
L * = DPPBA - 1
(L1a)
L * = DPPBA - 1
(L1a)
L * = DPPBA - 1 (L1a)
R = H [126]
R = H [126]
R = H, R
1
= CH
3
[126]
R = H [127]
O
O
O
O
O
O
OO
Ph
OMe
83% ee (90%)
L * = BINAP (L23a)
94% ee (93%)
L * = Ph - DIAPHOX
(L18)
85% ee (99%)
89% ee (92%)
L * = BINAP
(L23a)
L * = BINAP
(L23a)
R
1
= Ph [129]
R = Ph [128]
R = Ph [128]
R = Ph [128]
a
If not stated otherwise, R
1
= H, X = OAc.
Me
3
Si
Si Me
3
Ph
N
N
R'
N
O
P
O
N
N
H
PPh
2
Ph
P
P
O
PPh
2
N
O
N
Pd
R'
P
Ph N
R
N
Ph
N
Ph
Me
3
Si
Si Me
3
H
Ph
R''
Ph-DIAPHOX
(
L1 8
)
AcO
QUIPHOS
(
L2 4
)
(
R
)-
BINAP
(
L23a
)
Figure 8B.12.
Some of the ligands and proposed allyl complexes used for allylic alkylations with
prochiral
β
- keto esters and
β
- diketones.
The Trost group also achieved very high enantio- and diastereoselectivity, up to 99%
ee and dr
98:2, respectively, with cycloalkenyl and 1,3-dimethylallyl carbonates as
substrates [126] .
≥
8B.2.2.4.2.
-Cyanopropionic Acid Derivatives and Related Pronucleophiles
Good
results in this area were obtained by Ito et al. with their ferrocene ligand
L25
with a
coordinating side arm (Fig. 8B.13) [130]. Truly spectacular results were achieved in an
unusual way, by stereocontrol via the nucleophile with a chiral Rh complex coordinating
to the cyano group [131]. This was accomplished with a bimetallic catalyst system con-
sisting of Rh(acac)(CO)
2
, Pd(Cp)(
α
- C
3
H
5
) and the ligand
AnisTRAP
(
L26
), which was
previously developed by the Ito group (Scheme 8B.31 , Fig. 8B.13 , and Table 8B.15 ).
π
